Have you tried https://developers.google.com/sketchup/docs/ourdoc/image#path ?

Thanks - works perfectly.

cheers

@adamb said:

@thomthom said:

I did that for Vertex Tools, I take the average normal of the faces connected to the vertex.

You're missing a step with your averaging there. You need to weight by the contribution each face connected to the vertex makes - ie weight by the interior angle otherwise a cube constructed of triangles will end up with vertex normals not all pointing out exactly at 45 degrees.

How does one do that?

The default material is 'nil'.
So face.material=nil makes face have no material
and face.back_material=nil makes face have no back material
You can get the color used for the two types of default face material from
model.rendering_options["FaceFrontColor"]
and
model.rendering_options["FaceBackColor"]
which both return a Color object, you can then get its RGB values in the normal way etc...
You can also set these vales to a new color with []=
🤓